1. Field of the Invention
The present invention relates to a field effect transistor employing an amorphous oxide.
2. Related Background Art
In recent years, flat panel display (FPD) is commercialized as the results of progress of liquid crystal techniques, electroluminescence (EL), and the related techniques. The FPD is driven by an active matrix circuit comprising a field-effect thin film transistor (TFT) employing an amorphous silicon thin film or polycrystalline silicon thin film as the active layer formed on a glass substrate.
For smaller thickness, lighter weight, and higher impact strength of the FPD, use of a lightweight and a flexible resin substrate is investigated in place of the glass substrate. However, the transistor employing the silicon thin film cannot by directly formed on a less heat-resistant resin substrate, since the production of the silicon thin film transistor requires a relatively high-temperature in the process.
Therefore, for the TFT, use of an oxide semiconductor thin film such as a ZnO thin film is actively investigated which enables film formation at a lower temperature (Japanese Patent Application Laid-Open No. 2003-298062).
However, a transistor has not been obtained which satisfies simultaneously all of the properties of transparency and electric properties of the TFT, properties of the gate-insulating film, prevention of current leakage, and adhesiveness between the active layer and the substrate.